Event Filtering Idea

Example.java

package filter;

import java.util.Collection;

import filter.CauseFilters.All;
import filter.CauseFilters.First;
import filter.DataFilters.HasDouble;
import filter.DataFilters.HasInt;
import filter.SubtypeFilters.Exclude;

public class Example {

    //The Current methods
    @Listener
    public void onSubEvent(SubEvent event) {
        // Fairly typical pattern
        Optional<Player> player = event.getCause().first(Player.class);
        if(player.isPresent()) {
            //do something
        }
    }
    
    //==========================================================================
    //The proposed methods

    @Listener
    public void onSubEvent2(SubEvent event, @First Player player) {
        //will only be called if there is a player
    }

    @Listener
    public void onSubEvent2(SubEvent event, @First(name=NamedCause.NOTIFIER) Player player) {
        //will only be called if there is a player notifier present
    }

    @Listener
    public void onSubEvent3(SubEvent event, @First @HasDouble(key="health", value=5.0) Player player) {
        //will only be called if there is a player and they have 5 health
        // (at least thats the idea, still working on how to make data based filtering sane)
    }

    @Listener
    public void onSubEvent3(SubEvent event, @First @HasString(key="displayName", value="gabizou") Player player) {
        //will only be called if its gabizou
    }

    @Listener
    public void onSubEvent3(SubEvent event, @First @Supports(HealthData.class) Entity entity) {
        //will only be called if there is an entity and it has health
        //    (sure you could just use '@First Living entity' but its an example damn it)
    }

    @Listener
    public void onSubEvent3(SubEvent event, @First @Has(ChargedData.class) Creeper entity) {
        //will only be called if there is a creeper and its charged
        //    (this will be a bit of special handling to check the boolean state of the data as well as its existance)
    }

    @Listener
    public void onSubEvent2(SubEvent event, @All Player[] players) {
        //do something with all players
        //this will not be called if there are no players
    }

    @Listener
    public void onSubEvent2(SubEvent event, @All(allowEmpty=true) Collection<Player> players) {
        //do something with all players
        //this will be called regardless of if there are any players
    }
    
    @Listener
    public void onSubSub2And3(@Exclude(SubSubEvent1.class) SubEvent event) {
        // runs for SubSubEvent2 and SubSubEvent3 but not SubSubEvent1
    }
    
    @Listener
    public void onSubSub2And3(@Include({SubSubEvent1.class, SubSubEvent2.class}) SubEvent event) {
        // runs for SubSubEvent1 and SubSubEvent2 but not SubSubEvent3
    }
    
    @Listener
    public void onCancelled(@IsCancelled SubEvent event) {
        // will only run if the event has been cancelled by a previous listener
    }
    
    static interface Event { }
    
    static interface SubEvent extends Event { }
    
    static interface SubSubEvent1 extends SubEvent { }
    static interface SubSubEvent2 extends SubEvent { }
    static interface SubSubEvent3 extends SubEvent { }
    
}